For many years it has been common to use nonwoven fabrics as a cover member, or facing layer, for products that are adapted to receive body discharges, such as disposable diapers, sanitary napkins, adult incontinent devices, wound dressings and the like. Such fabrics have typically been formed by air-laying, carding, spun bonding and the like, and it is known to post-treat such fabrics to provide strength and integrity, as by the application of binders or fiber entanglement, either mechanically or by the application of fluid forces. Since such fabrics are often formed of hydrophobic material, it is also known to post-treat such fabrics with surface active agents to promote the passage of body discharges through the fabric. Such fabrics have, or are perceived to have, desirable characteristics such as breathability, drapeability, softness, and pleasant hand and tactile impression.
One of the drawbacks associated with facing layers formed of a nonwoven fabric is that liquid, such as urine, menses, wound exudate, and the like, that passes through the facing layer and into the absorbent core has a tendency to strike back through the facing layer, particularly under pressure and when the liquid in the absorbent core approaches the volumetric storage capacity of the core. For this reason, and other reasons, it has been known in the past to utilize apertured plastic films as the facing layer in absorbent articles.
The following list includes disclosures of such apertured films in issued U.S. and foreign patents and published patent applications.
U.S. Pat. No. 3,632,269--Doviak et al. PA1 U.S. Pat. No. 3,929,135--Thompson et al. PA1 U.S. Pat. No. 4,324,276--Mullane PA1 U.S. Pat. No. 4,351,784--Thomas et al. PA1 U.S. Pat. No. 4,381,326--Kelly PA1 U.S. Pat. No. 4,456,570--Thomas et al. PA1 U.S. Pat. No. 4,535,020--Thomas et al. PA1 U.S. Pat. No. 4,690,679--Mattingly et al. PA1 U.S. Pat. No. 4,839,216--Curro et al. PA1 U.S. Pat. No. 4,950,264--Osborn PA1 U.S. Pat. No. 5,009,653--Osborn PA1 U.S. Pat. No. 5,112,690--Cohen et al. PA1 U.S. Pat. No. 5,342,334--Thompson et al. PA1 U.S. Pat. No. 5,352,217--Curro PA1 U.S. Pat. No. 5,368,910--Langdon PA1 U.S. Pat. No. 5,368,926--Thompson et al. PA1 U.S. Pat. No. 5,376,439--Hodgson et al. PA1 U.S. Pat. No. 5,382,245--Thompson et al. PA1 U.S. Pat. No. 5,382,703--Nohr et al. PA1 U.S. Pat. No. 5,383,870--Takai et al. PA1 U.S. Pat. No. 5,387,209--Yamamoto et al. PA1 EP 0 304 617--Suda et al. PA1 EP 0 432 882 A2--Shipley PA1 EP 0 598 204 A1--Garavaglia et al. PA1 EP 0 626 158 A1--Coles et al. PA1 EP 0 626 159 A1--Taki et al. PA1 EP 0 640 328--Tanaka et al. PA1 JP 3-286762 A--Yamamoto et al. PA1 WO 92/18078 A1--Colbert PA1 WO 93/15701 A1--Turi et al. PA1 WO 94/18926 A1--Perry PA1 WO 94/22408 A1--Langdon PA1 WO 94/28846 A1--Steiger et al. PA1 WO 95/00093 A2--Osborn et al.
While certain of such apertured films have functioned reasonably well for their intended purposes, the vast majority of such films have actual and perceived major deficiencies. For example, even though such apertured films may permit fluid to readily pass therethrough, and may minimize strike-back of such fluid, such apertured films nevertheless tend to have the appearance, feel and hand of a film, rather than a fabric. Such film-like characteristics are considered as a negative by the consumer, and thus absorbent products with apertured films as a facing layer have not met with widespread consumer acceptance.
Major improvements for apertured film facing layers for absorbent products are disclosed in commonly assigned, copending U.S. patent application Ser. Nos. 08/417,404 and 08/417,408 to Turi et al. filed Apr. 5, 1995 as a continuation and a division of Ser. No. 08/004,379, filed Jan. 14, 1993 as a continuation of Ser. No. 07/744,744, filed Aug. 14, 1991 (corresponding to publication WO 93/15701 A1 on the above list). In the above-mentioned Turi et al. applications, an apertured film, and methods and apparatus for forming the film, are disclosed which impart to the film physical characteristics like those of nonwoven fabrics. This is accomplished by supporting a film formed of stretchable thermoplastic polymeric material on localized support regions of a backing member, and directing a fluid in the form of high pressure, small diameter columnar jets against the upper surface of the film, so that unsupported portions of the film are directed downwardly between the support regions to cause the formation of micro-holes and fiber-like elements (fibrils) thereabout to impart to the apertured film physical characteristics of appearance, softness, feel and hand, like those of a nonwoven fabric. While such apertured films are a marked improvement over prior art apertured films, it is desired to provide further improvements in such apertured films, as by improving the ability of such films to pass viscous fluids, such as menses, and as by improving the ability of such films to wick or transport liquid through the thickness of the film (in the z-direction), and to then wick liquid away (in the x and y direction, particularly on the underside of the film, that is, the side of the film facing the absorbent core) from an initially wetted zone so as to promote more efficient utilization of the absorbent capacity of the entire absorbent core.
For use of apertured films as topsheets for sanitary napkins, clean-dry properties are very much desired. This means that the sanitary napkin should appear clean and dry to the user even after it has accepted a flow of menstrual fluid. There are many factors affecting the clean-dry properties of a sanitary napkin, including the aperture characteristics and open area of the napkin cover material. There is a trade-off in the effects of the film aperture size and open area on clean-dry properties. On the one hand, large apertures allow the fluid to be more rapidly transmitted to the absorbent core. On the other hand, apertures that are too large permit the fluid to be transported back through the topsheet from the absorbent core (a phenomenon sometimes referred to as "strike back") and to contact the wearer. Furthermore, large open areas tend to allow the stain on the absorbent core of the napkin to be visible through the topsheet and give the wearer the perception that the product has not kept her clean. To exhibit both clean and dry properties, a topsheet must have a carefully balanced combination of aperture size and open area: large enough apertures to rapidly accept a flow of menstrual fluid and to allow it to pass through to the napkin's absorbent core, but small enough to mask the stain on the underlying absorbent core to give the wearer the perception of cleanliness.